1. Field of the Invention
The present invention relates to an image processor for performing edge emphasis of an original image.
2. Description of the Prior Art
In an image processor, edge emphasis is performed with a digital filter in order to guarantee a resolution. The digital filter used is a secondary differential filter (Laplacian filter).
However, when the above-mentioned edge emphasis is performed, noise components at high frequencies are also emphasized, and this deteriorates image quality. On the other hand, if the above-mentioned edge emphasis is performed weakly in order to suppress emphasis of noise components, narrow lines and the like cannot be emphasized well. In order to solve this problem, edge emphasis is proposed which does not include adjacent pixels around a target pixel if the density of the target pixel is different from those of adjacent ones around the target one within a certain value. However, this approach has a problem that edge emphasis cannot be performed for a character region including hand-written characters of low densities wherein the densities thereof are not sufficiently large.